Added a version of draw_rectangle() that can draw directly onto an array2d.

dlib/image_transforms/draw.h

@@ -166,6 +166,46 @@ namespace dlib
         draw_line(p1.x(),p1.y(),p2.x(),p2.y(),c,val);
     }
 
+// ----------------------------------------------------------------------------------------
+
+    template <
+        typename image_type,
+        typename pixel_type
+        >
+    void draw_rectangle (
+        image_type& c,
+        const rectangle& rect,
+        const pixel_type& val
+    ) 
+    {
+        draw_line(c, rect.tl_corner(), rect.tr_corner(), val);
+        draw_line(c, rect.bl_corner(), rect.br_corner(), val);
+        draw_line(c, rect.tl_corner(), rect.bl_corner(), val);
+        draw_line(c, rect.tr_corner(), rect.br_corner(), val);
+    }
+
+// ----------------------------------------------------------------------------------------
+
+    template <
+        typename image_type,
+        typename pixel_type
+        >
+    void draw_rectangle (
+        image_type& c,
+        const rectangle& rect,
+        const pixel_type& val,
+        unsigned int thickness
+    ) 
+    {
+        for (int i = 0; i < thickness; ++i)
+        {
+            if ((i%2)==0)
+                draw_rectangle(c,shrink_rect(rect,(i+1)/2),val);
+            else
+                draw_rectangle(c,grow_rect(rect,(i+1)/2),val);
+        }
+    }
+
 // ----------------------------------------------------------------------------------------
 
     template <

dlib/image_transforms/draw_abstract.h

@@ -55,6 +55,29 @@ namespace dlib
 
 // ----------------------------------------------------------------------------------------
 
+    template <
+        typename image_type,
+        typename pixel_type
+        >
+    void draw_rectangle (
+        image_type& img,
+        const rectangle& rect,
+        const pixel_type& val,
+        unsigned int thickness = 1
+    );
+    /*!
+        requires
+            - image_type == is an implementation of array2d/array2d_kernel_abstract.h
+            - pixel_traits<pixel_type> is defined
+        ensures
+            - Draws the given rectangle onto the image img.  It does this by calling
+              draw_line() four times to draw the four sides of the rectangle.  
+            - The rectancle is drawn with the color given by val.
+            - The drawn rectangle will have edges that are thickness pixels wide.
+    !*/
+
+// ----------------------------------------------------------------------------------------
+    
     template <
         typename image_type,
         typename pixel_type